1. Field of the Invention
The present invention relates to safety devices for use during open-heart surgery for preventing air from entering into the patient's circulatory system. More specifically, the invention relates to a safety air diverter which is placed on the positive side of the blood pump.
2. Related Art
Since the inception of pump supported surgery, the threat of catastrophic pump accidents has continued to plague both surgeons and perfusionist alike. Reed and Stafford, in their text Cardiopulmonary By-Pass (Surgimedics/TMP 2nd Ed. 1985), have reported that during the six year period from 1972 through 1977, the number of injuries or deaths resulting from accidents was a conservative 1 per 1000.
Even though there have been some improvements made since that time, there have been other factors that have off-set these improvements. Increased caseload, inexperience, and increased number of tasks and responsibilities imposed upon the perfusionist, and changes in technique and equipment, are but a few of the reasons that have resulted in increased risks of pump accidents.
The most dreaded and most common result of these accidents is the introduction of air into the extracorporeal circuit. The attention which the perfusionist must devote to his or her previously-mentioned increased duties has distracted the perfusionist from his or her primary responsibility of insuring a proper reservoir level. One can easily see how this has ultimately increased the risk of accidentally permitting air to enter the arterial line.
Besides the emptying of the reservoir, there are other ways that air can enter the arterial line, including an oxygenator falling from the holder; an arterial line parting from the connector on the negative side of the pump head; a crack in a connector on the negative side of the pump head; a rupture of the tubing inside the arterial pump head; or any other phenomenon that may allow air to be drawn into the negative side and ultimately finding its way inside the human body.
There have been several attempts made throughout the history of open-heart surgery to address this air emboli issue. Gas bubble detectors, low level sensors, arterial filters, and arterial bubble traps, are a few of the attempts at addressing this problem. One example of such a device is the SILENT GUARD.TM. ball valve (Catalog No. SG-10) sold by American Omni Medical, Inc. of Costa Mesa, Calif. This ball valve is used on the negative side of the pump and incurs all of the disadvantages of any device which might be utilized on the negative side. Reed and Stafford commented on this ball valve as follows in Cardiopulmonary By-Pass: "There is one ball type valve on the market which is placed in-line between the arterial outlet connector and the arterial pump head [i.e., on the negative side of the pump] . . . . There is some controversy over the effectiveness of this device from 100% fool-proof safe on the one hand to being able to pump air past the device in a low flow rate situation. Regardless, the following has been reported and can occur extremely rapidly: The arterial blood level is lost, the ball check valve engages, gas is cavitated out of the blood and in the arterial line between the oxygenator and the pump head, blood returned to the arterial reservoir disengages the check valve and the gas bubbles are pumped into the patient. We do not believe that this device is the answer to the problem."
Thus, even though these prior art devices have improved upon the safety aspects of extracorporeal surgery, they certainly have not eliminated the risks. Reed and Stafford state in Cardiopulmonary By-Pass: "These authors are at a loss to understand why more safety devices have not appeared on the market. Certainly, manufacturing has been told about the need for these devices for the past eight to ten years". It is the solution of this and other problems to which the present invention is directed.